Environmental controls

Clinical description

Environmental controls reduce the risk of spreading TB by reducing the concentrations of infectious droplet nuclei suspended in room air. They are of secondary importance after administrative controls in the prevention of TB transmission. If administrative controls are inadequate, environmental controls will not eliminate the risk.

Environmental control measures include the following:

 Ventilation (natural, mixed-mode and mechanical) systems;

o Natural ventilation relies on open doors and windows to bring in air from the outside. This implies that IEC materials such as posters and window stickers are displayed as reminders and daily checks (up-to-date log books) are in place to make sure doors and windows are maintained in an open position to enhance ventilation. Unrestricted openings (that cannot be closed) on opposite sides of the room provide the most effective natural (cross) ventilation. Ideally, the unrestricted opening area should be 20% of the floor area.

o Electrical fans12 and wind-driven roof turbines – “Whirly birds” – used for mixed- mode ventilation systems may assist, not only to provide comfort, but also to mix the air and control the direction of airflow.

o Mechanical ventilation systems may be useful in specialized, identified high- risk TB containment laboratories where liquid culture procedures and drug- susceptibility testing are conducted.

 Filtration;

 GUV( Germicidal ultraviolet ) systems.